It seems to me that their 'performance' has 2 parts:
1) Their own bottom line. We don't know much about this, really. They say they broke ticket revenue records, and there is no reason not to believe them. There is no reason to believe them, either, as far as that goes. Along with their bottom line is attendance. Reference llama's post above - attendance up compared to 2 years ago, and probably last year when you factor in the end of the year always having higher attendance in the Phoenix market. The downside is that, compared to Glendale's figures, those attendance numbers included more than 1000 comp tickets every night. To me, they can give away as many as they want... It's their business. But if you try to evaluate their performance, you have to consider that.
2) How much revenue they returned to Glendale. This piece makes Glendale's financial situation part of the discussion. As has been mentioned, very roughly, by the time the supplemental surcharge is factored in, IA will return about 5.5M to Glendale this year. Since Glendale is paying 15M/yr, and this is a short year, Glendale will end up paying IA about 13.5M. Thus, this year cost Glendale about 8M for IA to manage the arena. They had budgeted 6M, so that is a 2M loss for Glendale. In a normal year, this would be a 3.5M loss, because of the full 15M being paid. So, IA performance in regard to Glendale: Not nearly as good as advertised. I would not say 'promised' because there were no guarantees.
That is all I will say at this point, because others have commented quite a bit on Glendale's situation in regard to their own financial situation.